1. Field of the Invention
The present invention generally relates to a method for jointing mitered frames using corner parts having new configurations. The present invention is equally directed to machines and apparatus for performing this method in order to permit the cutting and machining of several corner parts simultaneously.
2. Discussion of Prior Art
A number of models of corner parts are known which have different shapes, including square, rectangular, oval or cylindrical. Such corner parts are often formed of wood and are placed within mitered frames. Only the cylindrical parts, however, are used industrially. Such parts are referred to as journals and have both advantages and disadvantages.
There are a number of advantages. By using such a corner part only a single type of machining has to be performed on two parts to be jointed; machining will not weaken the wood members; it is easy to use drills having fixed interaxes; precision is increased; rigorous prepositioning of the parts will result; the joints can easily be standardized, with the drills or journals capable of being integrated into the machining assembly line; economies in the amount of wood are realized, the length of the parts being limited to the tenoning; the use of false pegs is permitted; it becomes possible to join curved wooden parts whose grain is cut; and it becomes possible to precisely position various pieces of disassembled furniture together, e.g., the side, the top, the bottom and partition.
There are also a variety of inconveniences, however. The use of journals requires a supplemental operation on a special machine; it is not possible to overcome machining which is not performed with a great deal of precision (i.e., frames having 45.degree. cuts in the profile); when large crosspieces are used the system will not prevent cracks caused by wood shrinkage; the journals are not suitable to join parts of small sections in which two journals cannot be housed in view of the minimum interaxis; it requires the use of calibrated journals and drilling without any play about the diameter of the journal; the journals must be driven into their housings by a hammer or gun; and it is impossible to simultaneously have perfectly calibrated journals and drilled holes without any play. When the journals are driven they cause a number of problems, including: divergent axes; caulked tips which prevent parallel driving, or even all jointing while requiring manual retouching of the journal tip; and in both of the latter cases, warped frames and shifting members result which cannot be overcome by mitering, particularly if the parts are profiled.
In addition to the above-noted faults caused by the journals themselves, drilling the journal housing is also delicate. If the machines used in drilling are precise, the drill bits used will not remain precise. In other words, at the beginning the drill bits will be perfectly concentric, as will be the chucks which are utilized. During machining, however, the drill bits become hot and therefore dull, thereafter warped, and thus no longer permit drilling without play. In fact, divergent or plunging drilling result which causes the frame elements or the veil (once mounted) to be uneven. Overcoming these faults is impossible. If it is really necessary a manual retouching can be performed, but this is a long and delicate process, particularly if the frames are profiled. As a result this procedure is quite onerous.